1. Field of the Invention
The present invention relates to a high strength coupling which transfers axial force and torque from one member to another via a key and keyway arrangement.
2. Description of the Prior Art
Many types of couplings have been used to connect one cylindrical member to another. In many instances, it is necessary to transfer axial force and torque from one shaft or pipe member to a second shaft or pipe member. Oftentimes, it is desirable that the coupling be easy to connect and disconnect which eliminates connecting the members by a permanent means such as welding.
Threaded couplings have been used to provide a quick connect/disconnect coupling. Threaded couplings transfer axial compressive and tensile forces and torque in one direction about the longitudinal axis. Threaded couplings have the disadvantage in that the threaded coupling will not take high torque loads in both the clockwise and counter-clockwise directions due to the threaded make-up of the coupling. Furthermore, the threaded coupling is extremely difficult to disconnect after prolonged periods of torque transfer due to the frictional engagement of the threads. Threaded couplings are also subject to damaged threads and cross-threading during the coupling make-up which can result in the replacement of the coupling member.
Various arrangements of keys and keyways have been used to form axial load and torque transferring couplings as, for example, shown in U.S. Pat. Nos. 4,893,962, 3,433,512, 3,315,993, 2,756,022, and 2,032,491. Typically, in key/keyway couplings, the key is subjected to shear stress both by the torque and the axial load. Shear stress is directly proportional to the cross-sectional area of the key in shear. The maximum design rating for the coupling is often limited by the shear stress of the key.
It is desirable to have a high strength coupling which can transfer both axial tensile and compressive forces and torque in both directions around the longitudinal axis of the connected members. The high strength coupling should be of simple construction, low cost and quick to connect and disconnect.